Determinants of Quantitative Optic Nerve Measurements Using Spectral Domain Optical Coherence Tomography in a Population-Based Sample of Non-glaucomatous Subjects

PURPOSE. To evaluate the ocular and systemic factors influencing measurements of optic nerve head (ONH) parameters and retinal nerve fiber layer (RNFL) thickness with spectral-domain optical coherence tomography (SD-OCT) in healthy Chinese adults. METHODS. Adults ranging in age from 40 to 80 years were consecutively recruited from the population-based Singapore Chinese Eye Study. A SD-OCT instrument was used to measure ONH and RNFL parameters. A total of 542 eyes from 542 non-glaucomatous Chinese subjects were analyzed. Univariable and multiple linear regression analyses were performed to examine the effects of a range of ocular (e.g., intraocular pressure [IOP], axial length [AL], disc area) and systemic (e.g., blood pressure, serum glucose) factors on ONH and RNFL parameters. RESULTS. In multiple regression analyses, neuroretinal rim area was independently associated with age (beta = -0.006, P < 0.001), disc area (beta = -0.183, P < 0.001), IOP (beta = -0.009, P = 0.008), AL (beta = -0.023, P = 0.004), and lens nuclear color (beta = 0.042, P = 0.001). Vertical cup-to-disc ratio was independently correlated with age (beta = 0.003, P < 0.001), disc area (beta = 0.207, P < 0.001), IOP (beta = 0.004, P = 0.014), AL (beta = 0.010, P = 0.008), and lens nuclear color (beta = -0.017, P = 0.006). Average RNFL thickness was independently related to age (beta = -0.204, P = 0.001), disc area (beta = 4.218, P < 0.001), signal strength (beta = 1.348, P < 0.001), and AL (beta = -1.332, P < 0.001). Disc area had the strongest effect on measurements of ONH parameters and RNFL thickness. CONCLUSIONS. In a non-glaucomatous population, optic nerve measurements with SD-OCT vary with disc area, age, IOP, AL, lens nuclear color, and signal strength, but systemic parameters have little influence. This information may be useful for interpretation of SD-OCT measurements. (Invest Ophthalmol Vis Sci. 2011; 52: 9629-9635) DOI: 10.1167/iovs.11-7481